Among 39 consecutive patients who underwent colectomy, mucosal proctectomy and ileo-anal anastomosis, a triplicated pelvic ileal pouch was constructed in 17, and a duplicated pouch in 22 patients. There was no mortality, but complications such as anastomotic dehiscence and pelvic sepsis led to removal of the pouch in seven patients (18 per cent). The functioning of the pouch and anal sphincter was assessed in 31 patients 6 months, and in 22 patients 12 months after closure of the diverting ileostomy. By 6 months, all patients were either completely continent or experienced only minor leakage and defaecation could be deferred for more than 15 min by 81 per cent of patients and flatus distinguished from faeces by 90 per cent of patients. No significant differences between triplicated and duplicated pouches were discernible at 6 months. At 12 months defaecation was significantly less frequent (P less than 0.05) in patients with triplicated pouches (median, 5 times in 24 h) than in patients with duplicated pouches (7 times in 24 h). All patients with triplicated pouches and all except one with duplicated pouches were able to defaecate spontaneously, without needing to intubate the reservoir. Thus, provided the early postoperative problems can be overcome, most patients achieve good anal function after mucosal proctectomy combined with a pelvic ileal reservoir. No evidence was found in this study that the functional results of duplicated pouches were superior to those of triplicated pouches; in fact, the triplicated pouches proved to be slightly superior.